Tian Yuchen [off-list ref] writes:

The 'pager_program' variable is currently defined as a file-scoped
static string in pager.c. Move it into 'struct repo_config_values'.

The configuration parsing logic remains strictly within pager.c to
respect subsystem boundaries. The read/write operations are simply
redirected to the repository-specific structure using
'repo_config_values()'.

By redirecting to repo_config_values(r), we now enforce that the
passed repository must be 'the_repository' (due to the assertion in
repo_config_values()).  All current callers of git_pager() and
check_pager_config() indeed pass 'the_repository', so this new
enforcement does not harm them.  However, it paves the way to later
lift the assertion and allow us to configure different pagers for
different repositories, which is a welcome improvement.

 static int core_pager_config(const char *var, const char *value,
 			     const struct config_context *ctx UNUSED,
-			     void *data UNUSED)
+			     void *data)
 {
-	if (!strcmp(var, "core.pager"))
-		return git_config_string(&pager_program, var, value);
+	struct repository *r = data;
+
+	if (!strcmp(var, "core.pager")) {
+		FREE_AND_NULL(repo_config_values(r)->pager_program);
+		return git_config_string(&repo_config_values(r)->pager_program, var, value);
+	}

It may be just me, but I would have preferred to see this written
more like


	if (!strcmp(var, "core.pager")) {
		struct repo_config_values *values = repo_config_values(r);

		FREE_AND_NULL(values->pager_program);
		return git_config_string(&values->pager_program, var, value);
	}

which will make it easier to see that we are freeing the same thing
immediately before we overwrite it.  It also shortens the lines.
For a temporary variable with a very short scope like this one that
is introduced solely for readability, it is OK to use even shorter
name like 'v' if you want to ('r' certainly has a much longer
lifespan that it, and I would probably have preferred to see it
called 'repo').

    Side note: we might want to give a hint in the coding guidelines
    document that a variable with larger lifespan should get longer
    names, or something.

Same here.

Same here.